A new study co-chaired by Sally Yates, the Obama administration's former deputy attorney general, and former Republican Congressman Trey Gowdy recommends doing away with mandatory minimum sentences and increasing parole opportunities to cut down on long prison sentences, which they say are often wasteful and ineffective.

That study, titled "How Long Is Long Enough?" was released Tuesday by the nonpartisan Council on Criminal Justice following a yearlong analysis of new and existing research.

Yates and Gowdy co-chair the CCJ's Task Force on Long Sentences, which also includes a retired chief justice of the Louisiana Supreme Court, former police and prison officials, a fellow at the conservative Heritage Foundation think tank, and a former director of the celebrated D.C. Public Defender Service.

The report's main takeaway is that "long" prison sentences, which it defines as 10 years or more, are financially wasteful and not more effective at deterring crime than shorter sentences.

The report contains 14 broad recommendations policymakers can use to reduce long sentences and, in general, make the U.S. carceral system more just, cost-effective and efficient.

"Some may wonder why would we even discuss the nation's use of long prison sentences now, amid a rise in homicide rates and legitimate public concern about public safety," Yates and Gowdy said in a joint statement Tuesday. "Because this is exactly the time to examine what will actually make our communities safer and our system more just."

"When crime rates increase, so do calls for stiffer sentencing, often without regard to the effectiveness or fairness of those sentences," they added. "Criminal justice policy should be based on facts and evidence, not rhetoric and emotion, and we should be laser-focused on strategies that make the most effective use of our limited resources."

Many of the report's recommendations focus on doing away with mandatory minimum sentences, especially in drug-related cases, and increasing parole opportunities and expanding prison programs proven to reduce recidivism, among other things.

Mandatory minimum sentences, which reduce a judge's discretion and impose prison sentences for certain crimes regardless of context, have been studied extensively since they were enshrined in law between the 1970s and 1990s.

"Overall findings indicate that mandatory minimums do not work as intended," the report says. "Decades of evaluations show that mandatory minimums fail to produce significant deterrent effects, are associated with increased racial disparities in sentencing, and can lead to the application of unduly harsh sentences in cases with compelling mitigating factors."

For those and many other reasons, the report recommends rolling back mandatory minimum sentence laws and giving judges more leeway to evaluate a case's context when imposing sentences.

The same goes for mandatory minimum sentences triggered by the amount of drugs offenders are caught with, the report says.

"Research suggests that this practice — fixing the prison sentences in law based on drug amounts — is neither an effective means to promote public safety nor a fair way to hold people accountable for the role they played in drug-based offending," it says.

Once individuals have been convicted and are in prison, the report recommends expanding good behavior time credit policies, which are not available for most prisoners serving long sentences.

"Decades of research and the experiences of both corrections professionals and incarcerated people show that both 'good' and 'earned' time policies offer" many benefits, like promoting safety within prisons, encouraging prisoners to enroll in vocational and educational opportunities, and engage in other types of programs "proven to promote ... positive post-release outcomes," the report says.

It also recommends that prisoners serving long sentences be given the same access to behavioral health programs as those serving shorter sentences. Those programs have a proven track record of "reducing conditions and behaviors associated with offending — including anxiety, depression, anger, and other symptoms associated with post-traumatic stress disorder," the report says.

With the money saved by reducing long prison sentences, the report says counties, judicial districts and other localities can then shift resources to "prioritize funding for violence reduction and victim and survivor services," such as "community-level, evidence-based strategies that prevent violence."

--Editing by Adam LoBelia.